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Within the diffusion description of mass transport in deeply inelastic collisions shell effects give rise to nonlinear drift coefficients. These are treated here using closure approximations for the set of equations for the variance and the mean mass. Application to238U+238U collisions is given. The central dip in theA1-potential screens the shell induced drift for small and medium energy loss and suppresses side peaks. As an example for asymmetric injection a model for136Xe+209Bi is discussed. Quite general, the particular shape ofU(A1) seems to be rather important for the interpretation of the data for all energy losses.

The final period of nuclear fission is discussed. We propose the following picture: Nuclear scission happens because of an hydrodynamic instability triggered by random surface vibrations. Thus the scissioning complex ruptures at random positions. Measured total kinetic energies point to the very relevance of the instability, while the randomness of rupture shows up in neutron emission data.

We study recent measurements of Ar+Mo reactions. Transport models do not agree with the data for large energy losses; they predict too small fluctuations and too much drift. Random neck rupture is however in keeping with experiments. We explain random neck rupture by very simple analysis and show that its basic ingredient, the critical ratio of total length over neck radius, is largely independent of angular momentum. We propose experiments to examine random rupture, one of them, a neutron multiplicity experiment, with a prediction of a saw-tooth structure.

Mass transport is described as a damped motion including inertia and a Gaussian stochastic force. The inertia coefficient is estimated in a hydrodynamical model, the damping coefficient by volume dissipation as well as by wall dissipation. Depending on the strength of the restoring force the mass-transfer degree of freedom may show inertia effects. In particular, underdamped motion cannot be excluded. The time development of the mean value t and the varianceGt is given in the overdamped as well as in the underdamped regime. The main effect of the inertia is a slower initial increase ofGt. A small-amplitude oscillatory behavior ofGt is possible in a moderately underdamped situation.

Correlation function formulae for transport coefficients of 2nd order in arbitrarily dense fluids are derived, using a modified Chapman-Enskog solution of the Liouville equation. Some static correlations are neglected. Approximate evaluation for dilute gases gives essentially the same results as the solution of Boltzmann's equation. As an application higher order transport effects in the critical region are estimated. It is conjectured that they are apparent in sound absorption and the line width of Rayleigh scattering if (T-Tc)/Tc?10-3.

The general solution of the equation of motion for the quantum mechanical distribu tion functionf2(r1P1,r2p2;t)in the two particle space is given by means of the Schrödinger scattering functions. A special initial condition leads to the usual Boltzmann equation plus density correction terms, which depend on the scattering matrixt(p',p). In the long wavelength limit and in lowest order oft(p',p) the Landau corrections to the simple Boltzmann streaming part are obtained.

Differential conservation laws for quantum mechanical operator fields are studied from a) some general point of view and b) to find the particle, momentum and energy conservation law, if the Hamiltonian isnot local as usually assumed. Concerning (b): If the interaction in a many body system is nonlocal, the particle current operator in the continuity equation has to be redefined. Physical properties of the interaction current are discussed. Similar nonlocal effects must be taken care of in the stress and energy current operator. Concerning (a): Besides the mentioned conservation laws there are arbitrary many other ones. In fact, for each arbitrary field a class of corresponding currents exists and vice versa, which together are related by a differential conservation law. Some physical aspects for defining current operators are given and discussed.

The effect of detuning on the linewidth of photon intensity correlation and the spectral linewidth is studied. This can be done by taking into account a general canonical momentum of the field strength in the fluctuation Hamiltonian. Detuning mainly affects the linewidths via threshold shift, but also explicitly by a reduction of the linewidths by $$(1 + \tilde \Delta ^2 )^{ - 1}$$ ( $$\tilde \Delta$$ proportional to detuning).

The free energy of a many-body system, classical as well as quantum mechanical, is represented by a finite Laplace transform of the interaction phase volume for stable potentials for which the thermodynamic limit exists. Possible singular and regular phase transitions are discussed with respect to the temperature dependence and are classified by the behaviour of a limiting density of complex temperature zeros. The phenomenologically known types are reproduced.

Quantum effects generate “channels” which guide a nucleus from ground state to scission. We present here the channels of258Fm and relate them to the measured kinetic energies of the fission products, to the mass asymmetry and to the relative abundance of the various fission components. The microscopic reason is discussed.